Moral moralizing

What if differences between people living in different cultures are actually much smaller than the differences in their cultures?

(Which would suggest a force other than culture that shapes humans. The obvious candidate is "biology", but it is not obvious how exactly biology translates into specific beliefs and actions, if not through the culture.)

What makes me consider this hypothesis? Mostly the fact that I sometimes better connect with people from another part of the world than with my neighbors. (Counter-argument: culture is not geography, maybe those people from another part of the world are actually culturally close to me. But this feels somewhat circular, as if the fact that I connect with someone is used as an evidence for sharing culture. Probably needs a more precise definition of what exactly counts as "culture".) Also, seems like many parts of culture are far-mode applause lights, that people more or less successfully compartmentalize.

I would be curious to hear an expert opinion on whether historically e.g. an average poor white person from South really considered slavery to be the right thing, or it was merely "someone else's problem" and "I can't do anything about it anyway". Kinda like I don't approve of Apple using foreign slave labor, but I don't see how I could realistically stop them. If I could make it go away simply by pressing a magical button, I would. What would an average person in the past do with the magical button?

When we learn about "opinions of people in the past", there is a risk we are listening to the ideologues of the past, not to the average people. Obviously, the ideologues believed their way of life was the morally superior one.

define "moralizing". I'm not sure what it is you think we maybe shouldn't do.

I would also point out that professional ethicists are if anything worse than ordinary people. Professional ethicists are the ones who prevented most of the kinds of studies, like human challenge trials, that could have made this pandemic much less bad. 

Let me be sure I understand what you're saying? If someone wants to argue on the internet that abortion should be prohibited by the criminal law, or that there isn't any moral obligation to be vegan, then I shouldn't moralize about the fact that I disagree with them? I mean, I can think of ways that you could maybe argue that point, I just want to make sure I understand you though.

Where do you get the opinion that slavery, genocide and rape are bad? Whatever the answer is seems to be a solid base for ethics in your eyes. And clearly that's not only professional ethicists who hold that opinion, and I doubt they even hold it in a higher proportion than other people.